I just read http://unix.derkeiler.com/Newsgroups/comp.unix.solaris/2008-... and it seems that they did not solve any problem at all; they don't allow overcommit, that's all. But they do not do anything else to compensate for the disadvantages this implies (this also have advantages, but not only)
You can do that by tuning Linux to have this behavior if you like it. In a Unix system, I don't thing this is the most desirable behavior in the general case...
I can't remember but I did sit in on a presentation about 15 years ago where they explained it. I lent the notes to a senior developer and never got them back.
It doesn't have an OOM killer. Even more remarkably a call to allocate memory can't fail, but it may not return either. When Solaris (well, SmartOS in my case) runs completely out of memory, all hell breaks loose.